(models) added castToUnsigned method
When called on ExprInt, simply set the size on the expression (since by
default all integers are printed as unsigned constants and interpreted
as signed only when necessary)
(models) change signature of TypeUtil.getSize to avoid NPE
Not sure why it was 'Integer' in the first place, changed to 'int' and
return 0 for expressions where the size doesn't matter
(vhdl) huge simplification to printIndexes
(transformation) refactoring visitExprList
(vhdl) minor improvement to HDLTyper and added explicit unsigned' cast
(vhdl) assert expects a boolean, not a std_logic
(vhdl) escape name of entity if necessary